This invention is directed to novel acrylate-based or methacrylate-based compositions which are preferably used as adhesives. More particularly, this invention is directed to novel methacrylate-based compositions which include relative effective amounts of chlorosulfonated polyethylene and graft polymers for substantially enhancing overall adhesive properties of the compositions.
A variety of patents (for example, U.S. Pat. Nos. 3,890,407 and 4,112,013 to Briggs, Jr. et al, 4,118,436 to Craven, 4,126,504 to Wolinski et al, 4,127,699 to Aumiller et al, 4,182,644 to Briggs, Jr. et al, 4,223,115 to Zalucha et al, 4,226,954 to Pelosi, 4,263,419 to Piestert et al, and 4,293,665 to Zalucha et al) teach generally that acrylate-based or methacrylate-based adhesives can be obtained from mixtures which include effective amounts of chlorosulfonated polymethylene. Briefly put, of the above-mentioned patents which disclose adhesive compositions, adhesive physical properties of such compositions are described either in terms of lap shear strength, or T-peel strength, or both. Some of these patents, moreover, specifically teach that other adhesive properties or preparative features of the therein disclosed compositions can otherwise become enhanced (for example, substantially no premixing of composition ingredients being necessary prior to use thereof; or relatively fast setting of the composition, and strong durable bonds being formed; or adhesion to oily metal surfaces) through inclusion of chlorosulfonated polyethylene therein.
As the following terms are used throughout this application, acrylate-based adhesives are based upon the chemical structure: ##STR1## and methacrylate-based adhesives are based upon the chemical structure: ##STR2##
When R is hydrogen, for example, the acrylate-based and methacrylate-based adhesives are based upon acrylic acid and methacrylic acid respectively; or, when R is a methyl group, the acrylate-based and methacrylate-based adhesives are based upon methyl acrylate and methyl methacrylate respectively.
Graft Co-polymers
Polymers comprising relatively long sequences or chains of at least two different monomers or monomeric units can have such chains linked together in a "block" or "graft" arrangement. A block arrangement is linear and is formed from at least two alternating monomeric units. The block arrangement, moreover, can further be formed from monomeric unit sequences which alternate (or repeat) in either an ordered or a random fashion. See U.S. Pat. No. 4,332,858 to Saitoh et al. Block or graft polymers are often referred to as co-polymers, terpolymers or multi-component polymers.
In the graft arrangement, one or more of such sequences are grafted onto a backbone of yet another sequence, such grafting usually taking place at each one of a plurality of grafting sites of the backbone. See, for example, Textbook of Polymer Science, 2nd Edition, by F. W. Billmeyer, Jr., published by Wiley-Interscience, a Division of John Wiley and Sons, Inc. (1971), at pp. 350-351. In the graft co-polymer art, when the backbone is a rubber or a rubber-like material and the grafted sequences are vinyl or acrylate- or methacrylate-based monomers, the backbones are often referred to as the "core" of the graft co-polymer. Sequences grafted onto the core form a "shell" around the core.
Such graft co-polymers, frequently referred to as resins, often take the form of a plurality of relatively small particles, especially when the rubber or rubber-like material or the grafted portions or both of these are crosslinked. Not all graft co-polymer resins have such a core-and-shell configuration (or morphology), however. Some, for example, may have a more continuous (i.e., homogeneous) microstructure which, quite often, takes the form of interpenetrating (yet distinct) polymer networks.
Graft co-polymer resins which have the core-and-shell configuration are currently primarily used as modifiers in certain polymer systems. For example, certain ABS (acrylonitrile-butadiene-styrene) or MBS (methacrylate-butadiene-styrene) resins, when added to PVC (polyvinyl chloride), are well-known impact-resistance or processability modifiers.
Graft-co-polymers, per se, are generally not added to adhesive compositions to augment or enhance the adhesive qualities thereof. For example, although U.S. Pat. No. 3,870,675 to Kusayama et al teaches (at column 2, lines 6-27) that an acrylate-based or methacrylate-based adhesive composition can include an ABS resin, the ABS resin therein is included primarily because of its rubber-like characteristics. Certain types of ABS resin, moreover, are well known rubber-like materials and, accordingly, are often used interchangeably with other rubber-like materials. Such types of ABS resin, furthermore, are known to be two-phase systems comprising inclusions of a rubber or a rubber-like phase in a continuous, glassy phase, wherein the continuous phase forms a matrix for the two-phase system. It is further well known that obtaining preferred rubber-like qualities, as to such types of ABS resin, requires selectively grafting, as between the continuous and rubber or rubber-like phases thereof. See, for example, Textbook of Polymer Science, cited above, at page 408. The '675 patent, accordingly, further mentions other compositions wherein other rubber or rubber-like materials have been substituted for ABS. (In the '675 patent, see column 2, lines 15-19 in connection with column 3, lines 42-45 and column 6, Table 3.) The adhesive compositions of the '675 patent have adhesive properties (such as, for example, tensile strength after contact, shear strength and impact strength) which render the '675 adhesives substantially different (e.g., as to application or use) from the chlorosulfonated polyethylene-based compositions mentioned above.
Yet another patent, U.S. Pat. No. 4,287,106 to Forgo et al, discloses an acrylate-based or methacrylate-based adhesive composition including ABS polymers (see column 2, lines 33-48), but specifically teaches away from inclusion therein of chlorosulfonated polyethylene (column 1, lines 14-34 in connection with: column 1, lines 57-68; column 2, lines 1-32; column 8, lines 41-56; and column 9, lines 50-64). More specifically, the '106 patent teaches that a chlorosulfonated amide or imide, instead of chlorosulfonated polyethylene, produces an adhesive composition having certain desirable adhesive qualities or properties.
Up until the present time, moreover, it was thought that addition of rubber or rubber-like polymers, such as ABS, to acrylate-based or methacrylate-based adhesive compositions would enhance a first class (or group) of adhesive properties of the compositions, but that further addition (or inclusion) of an additional ingredient (or component) such as, for example, a chlorosulfonated polyethylene (so as to enhance a second class or group of adhesive properties of the composition) would probably render relatively less effective the first group of adhesive properties or would otherwise undesirably affect the overall adhesive performance of the composition. The '106 patent to Forgo, discussed above, accordingly, specifically teaches away from such a combined inclusion of ABS polymers and chlorosulfonated polyethylene in an acrylate-based or methacrylate-based adhesive composition.